Last month NPR's David Schultz reported about a 2009 outbreak of mumps among Orthodox Jewish communities in and around New York City. Many of the children who got sick had received the standard two-shot immunization. The New York Department of Public Health and the federal Centers for Disease Control tried giving a third shot to children who hadn't yet gotten sick.

But when Schultz wanted to report on whether the extra vaccinations had worked, and whether there were any side effects, he couldn't. He ran up against an embargo imposed by the journal Pediatrics. When articles ran in two other journals, Schultz was able to report on the outbreak and the extra vaccinations. But he could not answer an obvious question: Did the extra vaccinations work? Only after Pediatrics ran the article in question was he able to later report the results.

If you worry about how embargoes affect journalists' access, you may want to follow Embargo Watch,[2] by Ivan Oransky, executive editor at Reuters Health.